Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	$ 12,309	$ 18,563	$ 18,072	$ 13,052
OCI before reclassifications	(607)	(2,554)	(7,843)	4,949
Deferred income tax benefit (expense)	101	394	1,581	(1,273)
AOCI before reclassifications, net of income tax	11,803	16,403	11,810	16,728
Amounts reclassified from AOCI	175	(500)	264	(592)
Deferred income tax benefit (expense)	(35)	133	(56)	148
Amounts reclassified from AOCI, net of income tax	140	(367)	208	(444)
Balance, end of period	12,111	16,036	12,111	16,036
Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	17,535	21,759	22,217	18,283
OCI before reclassifications	(633)	(2,212)	(6,512)	2,674
Deferred income tax benefit (expense)	208	190	1,584	(785)
AOCI before reclassifications, net of income tax	17,110	19,737	17,289	20,172
Amounts reclassified from AOCI	(91)	(64)	(76)	(297)
Deferred income tax benefit (expense)	22	41	18	87
Amounts reclassified from AOCI, net of income tax	(69)	(23)	(58)	(210)
Balance, end of period	17,063	19,714	17,063	19,714
Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	1,073	4,154	1,513	1,698
OCI before reclassifications	442	(846)	(172)	2,202
Deferred income tax benefit (expense)	(102)	207	39	(461)
AOCI before reclassifications, net of income tax	1,413	3,515	1,380	3,439
Amounts reclassified from AOCI	236	(457)	279	(359)
Deferred income tax benefit (expense)	(54)	97	(64)	75
Amounts reclassified from AOCI, net of income tax	182	(360)	215	(284)
Balance, end of period	1,595	3,155	1,595	3,155
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(4,463)	(5,382)	(3,795)	(4,927)
OCI before reclassifications	(421)	507	(1,168)	76
Deferred income tax benefit (expense)	(4)	(4)	(40)	(28)
AOCI before reclassifications, net of income tax	(4,888)	(4,879)	(5,003)	(4,879)
Amounts reclassified from AOCI	0	0	0	0
Deferred income tax benefit (expense)	0	0	0	0
Amounts reclassified from AOCI, net of income tax	0	0	0	0
Balance, end of period	(4,742)	(4,879)	(4,742)	(4,879)
Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning of period	(1,836)	(1,968)	(1,863)	(2,002)
OCI before reclassifications	5	(3)	9	(3)
Deferred income tax benefit (expense)	(1)	1	(2)	1
AOCI before reclassifications, net of income tax	(1,832)	(1,970)	(1,856)	(2,004)
Amounts reclassified from AOCI	30	21	61	64
Deferred income tax benefit (expense)	(3)	(5)	(10)	(14)
Amounts reclassified from AOCI, net of income tax	27	16	51	50
Balance, end of period	(1,805)	$ (1,954)	(1,805)	(1,954)
MetLife Hong Kong
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax				(248)
MetLife Hong Kong | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax				(248)
MetLife Hong Kong | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax				0
MetLife Hong Kong | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax				0
MetLife Hong Kong | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax				$ 0
Disposal Group, Held-for-Sale or Disposed of by Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	168		93
Disposal Group, Held-for-Sale or Disposed of by Sale | Unrealized Investment Gains (Losses), Net of Related Offsets
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	22		(168)
Disposal Group, Held-for-Sale or Disposed of by Sale | Unrealized Gains (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	0		0
Disposal Group, Held-for-Sale or Disposed of by Sale | Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	146		261
Disposal Group, Held-for-Sale or Disposed of by Sale | Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified from AOCI, net of income tax	$ 0		$ 0